<template>
<div class="music-list">
        <div class="back" @click="back">
                <i class="icon-back"></i>
        </div>
        <h1 class="title" v-html="title"></h1>
        <div class="bg-image" :style="bgStyle" ref="bgImage">
          <div class="play-wrapper">
            <div class="play" v-show="songs.length>0" ref="playBtn" @click="random">
              <i class="icon-play"></i>
              <span class="text">随机播放全部</span>
            </div>
          </div>
          <div class="filter" ref="filter"></div>
        </div>
        <div class="bg-layer" ref="layer"></div>
        <scroll
        :data="songs"
        class="list"
        ref="list"
        :probe-type="probeType"
        :listen-scroll="listenScroll"
         @scroll="scroll">
          <div class="song-list-wrapper">
                  <song-list :rank="rank" :songs="songs"  @select="selectItem"></song-list>
          </div>
          <div class="loading-container" v-show="!songs.length">
              <loading></loading>
          </div>
        </scroll>
</div>
</template>
<script type="text/ecmascript-6">
import Scroll from 'base/scroll/scroll'
import SongList from 'base/song-list/song-list' // 滚动偏移距离
import Loading from 'base/loading/loading'
import {prefixStyle} from 'common/js/dom'
import {mapActions} from 'vuex'
import {playlistMixin} from 'common/js/mixin'
const transform = prefixStyle('transform')
const backdrop = prefixStyle('backdrop-filter')
const RESERVED_HEIGHT = 40
export default {
  mixins: [playlistMixin],
  data() {
    return {
      scrollY: 0
    }
  },
  props: {
    bgImage: {
      type: String,
      default: ''
    },
    songs: {
      type: Array,
      default: () => {
        return []
      }
    },
    title: {
      type: String,
      default: ''
    },
    rank: {
      type: Boolean,
      default: false
    }
  },
  computed: {
    bgStyle() {
      return `background-image:url(${this.bgImage})`
    }
  },
  created() {
    this.probeType = 3
    this.listenScroll = true
  },
  mounted() {
    this.imageHeight = this.$refs.bgImage.clientHeight
    this.minTranslateY = -this.imageHeight + RESERVED_HEIGHT // 最远滚动位置，不超过minTranslateY
    this.$refs.list.$el.style.top = `${this.imageHeight}px`
  },
  methods: {
    handlePlaylist(playlist) {
      const bottom = playlist.length > 0 ? '60px' : ''
      this.$refs.list.$el.style.bottom = bottom // 底部播放器适配
      this.$refs.list.refresh() // 强制scroll重新计算
    },
    scroll(pos) {
      this.scrollY = pos.y
    },
    back() {
      this.$router.back()
    },
    selectItem(item, index) {
      this.selectPlay({
        list: this.songs,
        index
      })
    },
    random() {
      this.randomPlay({
        list: this.songs
      })
    },
    ...mapActions([
      'selectPlay',
      'randomPlay'
    ])
  },
  watch: {
    scrollY(newY) {
      // console.log('newY' + newY)
      // console.log(this.minTranslateY)
      let translateY = Math.max(this.minTranslateY, newY) // 最大滚动量
      this.$refs.layer.style[transform] = `translate3d(0, ${translateY}px, 0)`
      // this.$refs.layer.style['transform'] = `translate3d(0, ${translateY}px, 0)`
      // this.$refs.layer.style['webkitTransform'] = `translate3d(0, ${translateY}px, 0)`
      // 滚动到顶部时，图片遮住文字
      let zIndex = 0
      if (newY < this.minTranslateY) {
        zIndex = 10
        this.$refs.bgImage.style.paddingTop = 0
        this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
      } else {
        this.$refs.bgImage.style.paddingTop = '70%'
        this.$refs.bgImage.style.height = 0
      }
      this.$refs.bgImage.style.zIndex = zIndex
      // 滚动到顶部按钮消失
      if (newY < this.minTranslateY) {
        this.$refs.playBtn.style.display = 'none'
      } else {
        this.$refs.playBtn.style.display = ''
      }
      // 列表从初始位置向下滚动时，图片随着滚动实现缩小放大
      let scale = 1
      let blur = 0
      const percent = Math.abs(newY / this.imageHeight)
      if (newY > 0) {
        scale = 1 + percent
        zIndex = 10
      } else {
        blur = Math.min(20 * percent, 20)
      }
      this.$refs.filter.style[backdrop] = `blur(${blur}px)`
      // this.$refs.filter.style['backdrop-filter'] = `blur(${blur}px)`
      // this.$refs.filter.style['webkitBackdrop-filter'] = `blur(${blur}px)`
      this.$refs.bgImage.style[transform] = `scale(${scale})`
      // this.$refs.bgImage.style['transform'] = `scale(${scale})`
      // this.$refs.bgImage.style['webkitTransform'] = `scale(${scale})`
      this.$refs.bgImage.style.zIndex = zIndex
    }
  },
  components: {
    Scroll,
    SongList,
    Loading
  }
}
</script>
<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable';
@import '~common/stylus/mixin';

.music-list {
  position: fixed;
  z-index: 100;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  background: $color-background;

  .back {
    position: absolute;
    top: 0;
    left: 6px;
    z-index: 50;

    .icon-back {
      display: block;
      padding: 10px;
      font-size: $font-size-large-x;
      color: $color-theme;
    }
  }

  .title {
    position: absolute;
    top: 0;
    left: 10%;
    z-index: 40;
    width: 80%;
    no-wrap();
    text-align: center;
    line-height: 40px;
    font-size: $font-size-large;
    color: $color-text;
  }

  .bg-image {
    position: relative;
    width: 100%;
    height: 0;
    padding-top: 70%;
    transform-origin: top;
    background-size: cover;

    .play-wrapper {
      position: absolute;
      bottom: 20px;
      z-index: 50;
      width: 100%;

      .play {
        box-sizing: border-box;
        width: 135px;
        padding: 7px 0;
        margin: 0 auto;
        text-align: center;
        border: 1px solid $color-theme;
        color: $color-theme;
        border-radius: 100px;
        font-size: 0;

        .icon-play {
          display: inline-block;
          vertical-align: middle;
          margin-right: 6px;
          font-size: $font-size-medium-x;
        }

        .text {
          display: inline-block;
          vertical-align: middle;
          font-size: $font-size-small;
        }
      }
    }

    .filter {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(7, 17, 27, 0.5);
    }
  }

  .bg-layer {
    position: relative;
    height: 100%;
    background: $color-background;
  }

  .list {
    position: fixed;
    top: 0;
    bottom: 0;
    width: 100%;
    // overflow: hidden;
    background: $color-background;

    .song-list-wrapper {
      padding: 20px 30px;
    }

    .loading-container {
      position: absolute;
      width: 100%;
      top: 50%;
      transform: translateY(-50%);
    }
  }
}
</style>
